Generally speaking, this invention relates to the manufacture of optical lenses for application, among others, as eye glasses and contact lenses.
Lenses have generally been formed with spherical surfaces due to the convenience of grinding. An aspheric surface would be difficult and expensive to produce by conventional methods such as a numerically controlled lathe. However, conventional lenses provide several disadvantages. In the case of contact lenses, the cornea is aspheric, yet most contact lenses are formed with a spherical inner surface producing irregular tear layers and localized bearing areas. With the development of a device for extending the range of a keratometer to permit measurement of the curvature of a cornea at different radial positions, as taught in our U.S. Pat. No. 3,609,017, accurate knowledge of the shape of the cornea is available, permitting the design of contact lenses having an aspheric inner surface were a convenient method of manufacture available. Further, it has proved difficult to provide cylindrical corrections for dealing with astigmatism and a bifocal capability in contact lenses.
The foregoing deficiencies in the prior art are avoided by the methods and apparatus in accordance with the invention.